Many digital versatile discs (DVD) and Blu-ray (registered trademark) discs (BD) are utilized as information recording media that record various content, such as movie and music.
A BD-ROM, which is a medium that records content such as movie in advance, records data such as audio and subtitle, as well as a high definition (HD) image which is a high quality image, for example. The current BD-ROM mainly records an HD image, which is what is called a high definition television compatible 2K image in many cases, but it is envisaged that the quality of the image is enhanced in future, and the media that record an ultra high definition image (UHD) increase.
Note that representative examples of the ultra high definition image (UHD image) are high resolution images such as 4K and 8K for example, but are not limited to these high resolution images, and a high dynamic range image whose output brightness level is expanded, an image of a wide output color space, and the like are also referred to as UHD image. It is envisaged that the media that record this UHD image increase in future. Note that a data record reproduction process that utilizes the BD and the 4K image are described in Patent Literature 1 (JP 2011-023071A) or the like, for example.
It is estimated that many high dynamic range (HDR) images that expand outputtable color and brightness ranges are utilized as the ultra high definition image (UHD image), for example. Note that the image of the past whose outputtable color and brightness ranges are narrower than the HDR image is referred to as standard dynamic range (SDR) image.
The HDR image has an expanded outputtable color and an expanded outputtable brightness range as compared with the past SDR image, and can output a more natural image which is the same as an actual scene seen with an eye of a person. For example, the outputtable color range of the SDR image is the color of sRGB color space within the range of the color space of the color space specification BT.1886 or BT.709. On the other hand, the HDR image is set to output the color of BT.2020 color space which is wider than BT.1886 and BT.709.
On the other hand, subtitle data that is superimposed and displayed on content such as a movie is, for example, timed text markup language (TTML) subtitle data. The TTML subtitle data is a subtitle data format specified by the World Wide Web Consortium (W3C) which is an international standardization organization of World Wide Web (WWW) utilization technology, and is subtitle data of an extensible markup language (XML) format that is configured to script the information indicating display timing of the subtitle together with the displayed subtitle data. Note that the TTML is described in Patent Literature 2 (JP 2012-169885A) for example.
However, this TTML subtitle data is specified as the data of 8-bit expression data in the sRGB color space. That is, the TTML subtitle data is output data in the same color space as the above SDR image. Thus, there is a problem that, if the TTML subtitle data is superimposed and displayed on HDR movie content for example, the SDR subtitle data is displayed on the HDR image, and a viewer feels difference in color and brightness between the image and the subtitle, and the viewer has a feeling of strangeness.